This invention pertains to a contact spring attached to an internal magnetic shield within a cathode-ray tube.
A color cathode-ray tube (CRT) typically has an internal magnetic shield to reduce the influence of magnetic fields on electron beam trajectories as a cathodoluminescent screen of the tube is scanned. The shield is usually made of 0.1 mm thick cold-rolled steel and is fastened to a shadow-mask frame so that the shield and frame are magnetically coupled. The magnetic shield is designed to fit into the funnel and be as close to the funnel wall as possible, but should not touch the funnel to avoid any friction between the shield and a conductive anode coating on the inner surface of the glass funnel.
It has been conventional practice to attach a flexible contact spring to the rear portion of the magnetic shield for effecting an electrical connection between the shield and the conductive coating on the inner surface of the funnel. One means of attaching the contact spring to the magnetic shield is by welding, which tended to erratically produce splatter. The resultant loose particles therefrom are detrimental to tube operation, such as by blocking apertures in the shadow mask or causing shorts and high-voltage arcing.
An improvement in the state of the art was disclosed in U.S. Pat. No. 4,310,779 wherein the contact spring has a wrap-around clip which is facily affixed to a fluting formed in the rear ledge of the magnetic shield. Such a contact spring does not firmly lock onto the magnetic shield, resulting in problems due to "loose" springs. The present invention provides a cooperative locking combination which firmly secures the contact spring to the magnetic shield.